On 11/13/2013 11:20 AM, Geert Uytterhoeven wrote:
> On Wed, Nov 13, 2013 at 4:51 PM, Rob Herring <robherring2@xxxxxxxxx> wrote:
>> On Tue, Nov 12, 2013 at 1:42 PM, Geert Uytterhoeven
>> <geert@xxxxxxxxxxxxxx> wrote:
>>> The different architectures used their own (and different) declarations:
>>>
>>> extern struct boot_param_header __dtb_start;
>>> extern u32 __dtb_start[];
>>> extern char __dtb_start[];
>>>
>>> Consolidate them using the first variant in <linux/of_fdt.h>.
>>> This requires adding a few "address of" operators on architectures where
>>> __dtb_start was an array before.
>>>
>>> Signed-off-by: Geert Uytterhoeven <geert@xxxxxxxxxxxxxx>
>>> Cc: Vineet Gupta <vgupta@xxxxxxxxxxxx>
>>> Cc: James Hogan <james.hogan@xxxxxxxxxx>
>>> Cc: Ralf Baechle <ralf@xxxxxxxxxxxxxx>
>>> Cc: Jonas Bonn <jonas@xxxxxxxxxxxx>
>>> CC: Chris Zankel <chris@xxxxxxxxxx>
>>> Cc: Rob Herring <rob.herring@xxxxxxxxxxx>
>>> Cc: devicetree@xxxxxxxxxxxxxxx
>>> ---
>>> arch/arc/include/asm/sections.h | 1 -
>>> arch/arc/kernel/setup.c | 2 +-
>>> arch/metag/kernel/setup.c | 6 +-----
>>> arch/mips/include/asm/mips-boards/generic.h | 4 ----
>>> arch/mips/lantiq/prom.h | 2 --
>>> arch/mips/netlogic/xlp/dt.c | 4 ++--
>>> arch/mips/ralink/of.c | 2 --
>>> arch/openrisc/kernel/setup.c | 2 +-
>>> arch/openrisc/kernel/vmlinux.h | 2 --
>>> arch/xtensa/kernel/setup.c | 3 +--
>>> include/linux/of_fdt.h | 3 +++
>>> 11 files changed, 9 insertions(+), 22 deletions(-)
>>
>> This is great, but I would like to see this taken one step further and
>> move the selection logic into the core code. We can try to use the
>> built-in dtb if early_init_dt_scan is passed a NULL or invalid dtb. This
>> should work for most arches I think and still allows an arch to do a
>> different selection algorithm if desired.
>
> Yes, that makes sense.
>
>> Are the DT related patches dependent on the rest of the series?
>
> Not really. There may be small rejects if you apply it out-of-order,
> but nothing serious.
>
>> Something like this is what I have in mind:
>>
>> diff --git a/drivers/of/fdt.c b/drivers/of/fdt.c
>> index 5c47910..723f854d 100644
>> --- a/drivers/of/fdt.c
>> +++ b/drivers/of/fdt.c
>> @@ -869,14 +869,16 @@ void * __init __weak
>> early_init_dt_alloc_memory_arch(u64 size, u64 align)
>>
>> bool __init early_init_dt_scan(void *params)
>> {
>> - if (!params)
>> - return false;
>> -
>> /* Setup flat device-tree pointer */
>> initial_boot_params = params;
>>
>> + if (!initial_boot_params ||
>> + (be32_to_cpu(initial_boot_params->magic) != OF_DT_HEADER))
>> + initial_boot_params = &__dtb_start;
>> +
>> /* check device tree validity */
>> - if (be32_to_cpu(initial_boot_params->magic) != OF_DT_HEADER) {
>> + if (!initial_boot_params ||
>
> initial_boot_params cannot be NULL here, so no need to check.
What about the case of no built-in dtb like on arm?
>
>> + (be32_to_cpu(initial_boot_params->magic) != OF_DT_HEADER)) {
>
> However, if __dtb_end == __dtb_start, you may be reading random
> data here from the next section. The OF_DT_HEADER check should cover
> this, but better safe than sorry?
Then we should also check that (__dtb_end != __dtb_start).
Rob
>
>> initial_boot_params = NULL;
>> return false;
>> }
>
> Gr{oetje,eeting}s,
>
> Geert
>
> --
> Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@xxxxxxxxxxxxxx
>
> In personal conversations with technical people, I call myself a hacker. But
> when I'm talking to journalists I just say "programmer" or something like that.
> -- Linus Torvalds
>
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